class_docstr: Defines the interface for metrics.
docstr: Creates a metric.
docstr_tok: ["Creates","a","metric","."]
code: def __init__(self, name: Text, prefix: Text = "Metrics"):
      """Creates a metric."""
      super(PyMetric, self).__init__(name)
      self._prefix = prefix
      self._summary_placeholder = None
      self._summary_op = None
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import abc
  from typing import Any, Optional, Sequence, Text, Union
  from absl import logging
  import numpy
  import six
  import tensorflow
  from tf_agents.metrics import tf_metric
  from tf_agents.trajectories import trajectory
  from tf_agents.typing import types
  from tf_agents.utils import common
label_desc: Use image node_id 1 to create a new PyMetric object from inherited base classes: tf with example: obj = PyMetric(name, prefix)